1. Field of the Invention
This invention relates to a recording apparatus with an ink jet recording head.
2. Related Background Art
There have been proposed various recording apparatuses for performing recording on recording media such as paper and OHP sheet (hereinafter referred to as recording paper or merely as paper). Such recording apparatuses have a recording head mounted on them and are of various recording systems, such as wire dot system, heat-sensitive system, heat transfer system and ink jet system.
Among these recording systems, there is an ink jet recording system. This system jets ink directly onto recording paper. Therefore, its running cost is inexpensive, and it is noted as a guiet recording system.
A recording apparatus which is based on such ink jet system generally uses a recording head having an arrangement of minute discharging orifices for jetting ink therefrom. Therefore, to cope with a case when ink becomes inadequate for jetting or recording due to such cause as intrusion of air bubbles or dust inwardly from such discharging orifices or viscosity increase of ink resulting from evaporation of ink solvent, it is a practice to flush the ink to remove these causes of defective jetting or discharging of ink (the process being referred to as jetting recovering process).
As one form of means for carrying out such jetting recovering process, there is a system, in which a cap capable of covering an orifice-formed face of a recording head and a pump in communication with the cap and providing an absorbing force thereto are provided. Ink-discharging energy generating elements are provided inside the discharging orifices and are driven to cause discharge of ink from all the discharging orifices to the cap (hereinafter the process being referred to as preliminary discharge). Also, they are driven to provide an absorbing force with the orifice-formed face closed by the cap, thus absorbing ink from the discharging orifices and thereby causing forced discharge of ink. In the above way, causes of defective discharge are removed along with ink (hereinafter the process being referred to as absorption recovering).
Further, in order to avoid adverse effects of dust or the like that are produced when the recording head is exposed to air by opening the cap, it is in practice to have the head closed with the cap after the power source is turned off or during waiting or when no data is provided from a host unit for a predetermined period of time (hereinafter the process being referred to as capping). This capping is liable to apply a pressure to the recording head to thereby move a carriage carrying the head. For this reason, it is necessary to open the cap after capping and effect position recognition, i.e., recognize the position of the carriage, when operating the carriage.
If the recognition of carriage position is not effected, it leads to failure of alignment of the discharging orifice position of the recording head, i.e., position of the carriage carrying the head, and position of the cap in the event of deviation of the carriage when it is intended to cap the discharge orifices. In such case, capping can not be effected, thus leading to such dificiencies as defective discharge of ink due to viscosity increase thereof or intrusion of dust or inability of ink absorption through the cap at the time of absorption recovery.
Thus, in the ink jet recording apparatus, it is very important to recognize the carriage position accurately in order to maintain the performance of the recording head for long time.
Heretofore, for recognizing the carriage position, a detection signal indicating that the carriage has passed by a particular position is recognized, and the recognition of position is effected with reference to the position corresponding to the recognition of the detection signal. In addition, for the recognition of the carriage position the detection signal is recognized once at the time of the closure of the power source, then the phase of exciting a stepping motor driving the carriage at this time is stored as reference position data, and subsequent recognition of the carriage position is effected through correction of the exciting phase of the stepping motor at the time of recognition of the detection signal provided when the particular position is subsequently passed by the carriage in comparison to the exciting phase stored as reference position data noted above.
In the former case, however, an error of one step is produced in the position recognition. Therefore, in case when capping is effected during recording, deviation by one line is liable to occur between the recording of upper line and that of lower line. In the latter case, no such error is produced owing to the correction according to the reference position data. However, although there is no problem so long as the carriage is run smoothly, in the event of occurrence of jumping of teeth of a motor drive system due to disturbance of the running of the carriage caused by external factors (such as jamming of paper), the stored reference position data becomes meaningless. Rather, in this case there is a possibility of increase of error in the carriage position recognition.
In a further aspect, in the recording apparatus of the type noted above, after the carriage is moved to the cap position, the output of the exciting phase of the drive motor, i.e., stepping motor, is stopped.
In such state without stepping motor exciting phase output, the carriage is freely movable by external forces. Therefore, when effecting capping with respect to the recording head mounted on the carriage, failure of moving the cap to a desired capping position is liable due to slight displacement of the carriage.
To overcome this drawback, it may be thought to secure the carriage in position by bringing the carriage into contact with a positioning member provided outside the recording zone and providing an urging force in this direction from a motor at all times. Doing so, however, produces a great load on the motor, giving rise to rupture of the motor and also consuming great power.
In a further aspect, an error in the position of the recording head is liable to be produced due to defectiveness of a detector for carriage position control or assembling errors of machine. In such cases, there will result a failure of alignment of the ink discharging orifice position of recording head, i.e., position of the carriage carrying the head, and cap position. This disables capping.
In this case, there are produced such dificiencies such as defective discharge of ink due to ink viscosity increase or introduction of dust.